I. Field of the Invention
The present invention relates generally to a system for detecting droplets on a translucent surface.
II. Description of Material Art
There are previously known systems for detecting droplets on a translucent surface. These previously known systems are typically used in the automotive industry for detecting raindrops on the windshield of a vehicle. Upon detection of the raindrops, the vehicle's windshield wipers are activated.
These previously known raindrop detectors in the automotive industry typically comprised one of two different types. In a first type, a light emitting diode (LED) having an output radiation emission in the infrared range was arranged in the automotive vehicle to direct the infrared emission towards a portion of the windshield. Reflected infrared radiation was then detected by an infrared detector. This reflected infrared radiation changes whenever raindrops are present on the windshield and these changes are detected by the infrared detector.
One problem associated with this previously known LED raindrop detector, however, is that the raindrop detector was unable to differentiate between raindrops and other marks on the windshield, such as debris, smudges, and the like. Consequently, when the raindrop detector was utilized to control the activation of the windshield wipers, these previously known systems were prone to activate the windshield wiper system when such activation was not desired. Furthermore, windshield coatings, such as ultraviolet coatings, often interfered with the operation of the detector.
In the second type of raindrop detector, an ultrasonic transmitter was effectively coupled to the windshield and, similarly, an ultrasonic receiver coupled to the windshield at a position spaced from the transmitter. In the event of the presence of raindrops on the windshield, the raindrops tended to dampen the ultrasonic vibration and such dampening is detected by the ultrasonic receivers.
This previously known raindrop detector, however, is disadvantageously costly to implement in the automotive industry. Furthermore, since the ultrasonic vibration transmitter necessarily involved a mechanical interface with the windshield, such mechanical interfaces were prone to failure.
A still further disadvantage of these previously known systems is that such systems were unable to detect the magnitude or number of raindrops.